It is expected that flexible display devices will be widely applied as portable scroll type displays or screen type large screen display devices. The realization of flexible display devices is strongly desired as next-generation display devices which are lightweight and have excellent storage capabilities. Recently, research and development into the flexibility of display devices is actively being performed. The research and development of flexibility of a liquid crystal display device (Liquid Crystal Display device (LCD)) as well as flexibility of a display device such as an Organic Light-Emitting Diode (OLED) or electronic paper is advancing.
In order to make a flexible display device, it is necessary to form a flexible substrate above a glass substrate, form an element forming a display device such as transistors and capacitors above the flexible substrate, and after forming the elements, peel the glass substrate off the flexible substrate (see Japanese Laid Open Patent Publication No. 2017-44714 and Japanese Laid Open Patent Publication No. 2017-44715). A resin substrate is used as a flexible substrate.
As disclosed in Japanese Laid Open Patent Publication No. 2017-44714 and Japanese Laid Open Patent Publication No. 2017-44715, when elements are formed above a resin substrate formed on a glass substrate, internal stress may be generated in the resin substrate. When the glass substrate is peeled off from the flexible substrate in this state, a display cell becomes distorted by the internal stress of the flexible substrate. In particular, the display cell is greatly distorted in the case when the difference between the internal stress in an array substrate and the internal stress in an opposing substrate is large. When the display cell is distorted, appearance defects such as wrinkles and warping occur in the display device when an optical member is attached to the display cell.